A Passive Optical Network (PON) is an access network that brings optical fibre cabling and signals all or most of the way to the end user in order to provide the end user with e.g. consumer broadband services.
A PON comprises an Optical Line Terminal (OLT) device. The OLT device is located at a central office of a service provider. A service provider may operate the PON to provide the consumer broadband services to the end user. The PON also comprises a number of Optical Network Units/Terminals (ONU/Ts) devices located near the end-users Terminals (TE) or Home Networks (HN). An Optical Distribution Network (ODN) comprising optical fibers and splitters may be used between the OLT device and the ONU/T devices in the PON in order to distribute traffic from the OLT device to the ONU/T devices and vice versa.
A Gigabit-Passive Optical Network (G-PON) is a PON capable of transmitting high bandwidths, i.e. in the order of gigabits per second (Gbps). Other PON networks may e.g. be ATM Passive Optical Network (APON), Broadband Passive Optical Network (BPON), Ethernet Passive Optical Network (EPON), Gigabit-Ethernet Passive Optical Network (GEPON), 10-Gbit/s Ethernet Passive Optical Network (10-G EPON), etc.
However, the configuration and operation of a G-PON is specified in the standards for G-PON.
In the G-PON standards, a list of alarm and Attribute Value Change (AVC) messages is specified. These alarm and AVC messages are generated by ONU/T devices in a G-PON in order to e.g. warn or indicate to an operator that a fault or error has occurred in the access network, or to indicate to an operator that an event has occurred in the ONU/T device causing the ONU/T device to change its operating state, i.e. a state change event, respectively. The alarm and AVC messages are sent by the ONU/T devices to the OLT device.
The OLT device is configured to receive and handle the alarm and AVC messages from the ONU/T devices in a centralized manner.
However, for large scale faults or in large scale deployments, i.e. implementations in which the OLT device may be connected to a large number of ONU/T devices, the OLT device may receive a large number of alarm and AVC messages concurrently. This may cause degradation in the performance of the OLT device.
An Alarm Report Control (ARC) procedure to control alarm messages sent from User Networks Interfaces (UNIs) operating on a Point-To-Point Protocol (PTPP) connected to a G-PON is defined in the standards G984.4 and G988. This ARC procedure may drop the sending of the alarm messages completely or for a specific time period.
However, firstly the ARC procedure only works on UNIs operating on a PTPP, or certain cardholders, that are connected to the G-PON, while many applications in the ONU/T devices also may generate alarm and AVC messages, such as, e.g. Session Initiated Protocol/Plain Old Telephone Service (SIP/POTS) applications, etc.
Secondly, the ARC procedure would also block the normal error report function in the ONU/ONT devices. The normal error report function is important to the access network management system in order to keep monitoring the network. Thus, the ARC procedure is not suitable for use in ONU/T devices.
A rate limit or bandwidth control in the upstream data traffic from the ONU/T devices to the OLT device may also be considered. However, this would only be able to cope with the situation when a single ONU/T device generates a large number of alarm or AVC messages. Normally, for large scale faults or in large scale deployments, the number of alarm and AVC messages generated by a single ONU/T device is limited and will thus most likely fall below the limit of the rate limit or bandwidth control.